The most important series of the regular season (to date) started Thursday night at Miller Park. The second-place Milwaukee Brewers are hosting the first-place Chicago Cubs for a crucial four-game series.

As an unbiased observer, Thursday's game was the first game this season that featured true postseason intensity. There were many edge-of-your-seat moments for fans of both teams. Ultimately, the Cubs walked way with a 5-3 win in 10 innings (box score) in the series opener.

The Brewers battled back from an early 2-0 deficit to tie the game on an Eric Sogard single in the seventh inning. Then, in the eighth, Eric Thames looped a single over the drawn in infield to give the Brewers a 3-2 lead. Alas, the one-run lead did not stand up. Javier Baez tied things up with a two-out, two-strike single back up the middle in the ninth. You can see the game-tying single here.

All-Star closer Corey Knebel was not available Thursday night due to his recent workload -- ace setup men Anthony Swarzak and Josh Hader were not available either because they've pitched so much this week -- so the save opportunity went to Jeremy Jeffress. He allowed the leadoff man to reach base on an infield single, then the game-tying single to Baez.

The Brewers had a golden opportunity to win the game in the bottom of the ninth, when they loaded the bases with one out. Cubs manager Joe Maddon went to closer Wade Davis with the game on the line, and Davis was able to strike out Domingo Santana for the second out of the inning. Santana got himself out by chasing high fastballs out of the zone. From Baseball Savant:

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Domingo Santana got himself out in the ninth inning by chasing up and out of the zone. Baseball Savant

After Santana struck out, Davis fell behind in the count 3-1 on Orlando Arcia, but battled back to get an inning-ending tapper back to the mound. Milwaukee had two chances to win the game in that ninth inning -- Santana could've won the game by making an out on a sac fly -- but they were unable to come through.

If you don't put the Cubs away when you have a chance, they're going to make you pay, especially when your top relievers are unavailable. Jon Jay doubled to start the 10th inning against Oliver Drake, then Kris Bryant gave the Cubs a 5-3 lead with a long two-run home run to dead center field. Drake caught way, way, way, too much of the plate with a fastball.

Weirdly, there's been a "Bryant is not clutch!" narrative floating around social media for much of the season. The reigning NL MVP put to rest any doubts about his clutchness Thursday night. That was a huge home run in a huge game for the Cubs.

With the win, the Cubbies are now 4 1/2 games up on the Brewers with 10 games to play. This was only the first game of a four-game series, so there are still three games to go this weekend, but Milwaukee is pretty much going to have to win all three to make this NL Central race interesting. Thursday's game was crucial, and it came down to the Cubs getting big hits at big moments and the Brewers being unable to do the same.